Add StackUsingLinkedList.java for #6715

[Kamal1023]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java
  Closes [FEATURE REQUEST] Add Stack Implementation Using Linked List in Java #6715
  This pull request adds a stack data structure implemented using a singly linked list. The StackUsingLinkedList class supports standard stack operations—push, pop, peek, isEmpty, and size - all in constant O(1) time complexity.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.69%. Comparing base (f0fb971) to head (a096583).

Files with missing lines	Patch %	Lines
...com/thealgorithms/stacks/StackUsingLinkedList.java	0.00%	28 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6740      +/-   ##
============================================
- Coverage     76.80%   76.69%   -0.12%     
  Complexity     6047     6047              
============================================
  Files           719      720       +1     
  Lines         20342    20370      +28     
  Branches       3940     3944       +4     
============================================
- Hits          15624    15622       -2     
- Misses         4127     4156      +29     
- Partials        591      592       +1     

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[github-actions]

This pull request has been automatically closed because its workflows or checks failed and it has been inactive for more than 14 days. Please fix the workflows and reopen if you'd like to continue. Merging from main/master alone does not count as activity.